In recent years, a power management system having a plurality of equipments, and a control apparatus which controls the plurality of equipments has been proposed (for example, Patent Literature 1). The plurality of equipments includes, for example, household electrical appliances such as air conditioners and illumination apparatuses, and distributed power sources such as photovoltaic cells, storage batteries, and fuel power generation apparatus. The control apparatus, for example, is referred to as HEMS (Home Energy Management System), SEMS (Store Energy Management System), BEMS (Building Energy Management System), FEMS (Factory Energy Management System), and CEMS (Cluster/Community Energy Management System).
For popularizing the above-described management system, generalization of the message format between the plurality of equipments and the control apparatus is effective, and such a generalization of the message format is being tested.